Head-mounted display

ABSTRACT

A head-mounted display including a transparent display, a liquid crystal lens and a first Fresnel lens is provided. The transparent display is configured to emit an image light beam. The liquid crystal lens is disposed near the transparent display. The transparent display is disposed between the liquid crystal lens and the first Fresnel lens. The first Fresnel lens is configured to receive an ambient light beam. The head-mounted display allows at least a part of the image light beam emitted from the transparent display passing through a pupil by phase modulating of at least a part of the liquid crystal lens.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 105102611, filed on Jan. 28, 2016. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a display device, and specifically relates to ahead-mounted display.

Description of Related Art

Currently, near eye display (NED) and head-mounted display (HMD) arekiller products during next generation. They have great potential fordevelopment. The NED is currently applied to augmented reality (AR) andvirtual reality (VR). In terms of VR, it is important to createrealistic in the virtual world in development. In terms of AR, thedevelopers focus on how to provide the best image quality within a thinand light device.

Furthermore, an image light beam used for display is emitted by aprojection device in a basic optical structure of a head mounted displaythat is used to actualize AR, the image light beam is then reflected bya semi-reflective semi-transmission optical device to enter into theuser's eyes. The light beam of the display image and the externalambient light beam all enter into the user's eyes to achieve the displayeffect of AR. However, in the above-mentioned structure, it isinevitable that the projection device appears in field of view (FOV) ofuser's eyes, and the above component occupies a certain space.Therefore, the viewing angle of the image displayed by the head mounteddisplay is greatly limited. In order to achieve a wide FOV effect, oneconventional solution is to reflect the image light beam multiple timesbased on a group of optical mirrors or a reflection system, thus, theprojection device can dispose outside of the FOV of user's eyes.However, the group of optical mirrors or the reflection system usuallyincreases the volume and the weight of the head mounted display, and aplurality of reflective surfaces of the group of optical mirrorsrequires extremely high precision in assembling and flatness. Otherwise,another conventional solution is to guide the image light beam from theprojection device to the user's eyes based on the light guiding memberhaving mutually bonded multilayer light splitting structure. However,the manufacturing process of the light guiding member includescomplicated processes such as coating, bonding, alignment, cutting andpolishing, consequently. Thus, it is more difficult to produce the lightguiding member. Therefore, it is one of the key points to achieve thewide FOV effect that reduce volume and weight of the head mounteddisplay and simplify the manufacturing process at the same time for thepeople in the related art.

The information disclosed in this “Description of Related Art” sectionis only for enhancement of understanding of the background of thedescribed technology and therefore it may contain information that doesnot form the prior art that is already known to a person of ordinaryskill in the art. Further, the information disclosed in the “Descriptionof Related Art” section does not mean that one or more problems to beresolved by one or more embodiments of the invention were acknowledgedby a person of ordinary skill in the art.

SUMMARY

The invention provides a head-mounted display being able to achieve wideFOV effect and having a smaller volume, a lighter weight, and asimplified manufacturing process.

The other objectives and advantages of the invention can be furtherunderstood through the technical features disclosed in the invention.

In order to achieve one of, a part of or all of the above-mentionedadvantages, or to achieve other advantages, an embodiment of theinvention discloses a head-mounted display including a transparentdisplay, a liquid crystal lens, and a first Fresnel lens. Thetransparent display is adapted to emit an image light beam. The liquidcrystal lens is disposed near the transparent display. The transparentdisplay is disposed between the liquid crystal lens and the firstFresnel lens. The first Fresnel lens is adapted to receive an ambientlight beam. The head-mounted display is adapted to allow at least a partof the image light beam emitted from the transparent display passingthrough a pupil by phase modulating of at least a part of the liquidcrystal lens.

Based on the above, the embodiments of the invention have at least oneof the advantages or effects below. In an embodiment of the invention,the transparent display of the head-mounted display is disposed betweenthe liquid crystal lens and the liquid crystal panel. The transparentdisplay is adapted to emit the image light beam, and the first Fresnellens is adapted to receive the ambient light beam. The head-mounteddisplay is adapted to allow at least a part of the image light beamemitted from the transparent display passing through a pupil by thephase modulating of at least a part of the liquid crystal lens.Therefore, the head-mounted display may emit the image light beam andreceive the ambient light beam at the same time, and the phasemodulating may occur in a part or in the entirety of the liquid crystallens to make the image light beam and the ambient light beam coexist andachieve the AR effect. Since the transparent display does not block theviewing angle, the head-mounted display may achieve wide FOV. Otherwise,the head-mounted display does not need to reflect the image light beammultiple times based on the group of optical mirrors or the reflectionsystem, thus, the volume of the head-mounted display becomes smaller andthe weight of the head-mounted display becomes lighter. Besides, thehead-mounted display does not need to guide the image beam through thelight guiding member having mutually bonded multilayer light splittingstructure, therefore, the manufacturing process of the head-mounteddisplay is simplified and it is easier to produce the head-mounteddisplay.

Other objectives, features and advantages of the present invention willbe further understood from the further technological features disclosedby the embodiments of the present invention wherein there are shown anddescribed preferred embodiments of this invention, simply by way ofillustration of modes best suited to carry out the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view depicting optical paths of a head-mounteddisplay in an embodiment of the invention.

FIG. 1B is another schematic view depicting optical paths of thehead-mounted display in the embodiment in FIG. 1A.

FIG. 2 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

FIG. 3A is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

FIG. 3B is another schematic view depicting optical paths of thehead-mounted display in the embodiment in FIG. 3A.

FIG. 4A is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

FIG. 4B is another schematic view depicting optical paths of thehead-mounted display in the embodiment in FIG. 4A.

FIG. 5 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

FIG. 6 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

FIG. 7 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. In this regard, directionalterminology, such as “top,” “bottom,” “front,” “back,” etc., is usedwith reference to the orientation of the Figure(s) being described.Accordingly, the drawings and descriptions will be regarded asillustrative in nature and not as restrictive.

FIG. 1A is a schematic view depicting optical paths of a head-mounteddisplay in an embodiment of the invention. Referring to FIG. 1A, in theembodiment, a head-mounted display 100 includes a transparent display110 and a liquid crystal lens 120 disposed near the transparent display110. To be more specific, the transparent display 110 is configured toemit an image light beam IL. The image light beam IL corresponds to animage signal from a processing device (not shown). The head-mounteddisplay 100 allows at least a part of the image light beam IL emittedfrom the transparent display 110 passing through a pupil P by the phasemodulating of at least a part of the liquid crystal lens 120. Forexample, the phase modulating occurs in at least a part of the liquidcrystal lens 120 of the head-mounted display 100 to make the dioptrebecome positive so as to allow at least a part of the image light beamIL emitted from the transparent display 110 passing through the pupil P.For example, the phase modulating of the liquid crystal lens means thatthe arrangement or the direction of the liquid crystal cells in theliquid crystal lens is adjusted by electric power so as to change thedirection of the light passed by the liquid crystal lens. The liquidcrystal lens can converge/diverge the light according to the adjustabledioptre of the liquid crystal lens. Besides, the degree of the phasemodulating means that rotating degree (30 degree or 60 degree) of thedirection of the liquid crystal cells, it is not limited thereto. In theembodiment, for example, the pupil P may be the pupil of user's eyes HE.The image light beam IL forms an image on the retina of the user's eyesHE after the image light beam IL passing through the pupil. However, inother embodiments, the pupil P may also be, for example, an aperture ofa general optical lens (like camera), the invention is not limitedthereto.

In the embodiment, a part of the area of the liquid crystal lens 120 iscorresponding to a part of the display area of the transparent display110. In other words, when the transparent display 110 displays a part ofthe display area, the liquid crystal lens 120 may be partially modulatedin accordance with the display area. Moreover, the phase modulating mayalso occur n the entire liquid crystal lens 120 to make the image lightbeam IL passed through the liquid crystal lens 120, and then the imagelight beam IL passes through the pupil P. To be more specific, thetransparent display 110 may emit the image light beam IL to form thecorresponding displayed image during the condition that the lighttransmitting state of the transparent display 110 is kept. Furthermore,at least a part of the ambient light beam AL passes through thetransparent display 110, the liquid crystal lens 120 and then passesthrough the pupil P. In other words, when the pupil P is, for example,the pupil of user's eyes HE, the image light beam IL emitted from thetransparent display 110 and at least a part of the ambient light beam ALmay all pass through the pupil P, so as to form an image on the retinaof user's eyes HE. Therefore, when the head-mounted display 100 isplaced in front of the user's eyes HE, both the image light beam IL andthe ambient light beam AL may pass through the pupil P of the user'seyes HE and the user may watch a virtual image (not shown in FIG. 1A)formed by the image light beam IL corresponding to the displayed imageand watch the image of the outside word (not shown in FIG. 1A)corresponding to the ambient light beam AL at the same time, so as toachieve the augmented reality effect. In the embodiment, the transparentdisplay 110 may be, for example, a thin film transistor-liquid crystaldisplay (TFT-LCD), an organic light-emitting diode (OLED) display, orother types of transparent displays, the invention is not limitedthereto.

Referring to FIG. 1A. In the embodiment, the head-mounted display 100further includes a first Fresnel lens 130 and a second Fresnel lens 140.The transparent display 110 is disposed between the liquid crystal lens120 and the first Fresnel lens 130, and the transparent display 110 isdisposed between the first Fresnel lens 130 and the second Fresnel lens140. Moreover, in the embodiment, the first Fresnel lens 130 may have anegative dioptre, and the second Fresnel lens 140 may have a positivedioptre. Specifically, the first Fresnel lens 130 is configured toreceive the ambient light beam AL. After being received by the firstFresnel lens 130, at least a part of the ambient light beam ALsequentially passes through the transparent display 110, the secondFresnel lens 140, and the liquid crystal lens 120 and then passesthrough the pupil P. In the embodiment, the transparent display 110emits the image light beam IL, and the image light beam IL may includean image light beam IL1 and an image light beam IL2, wherein the imagelight beam IL1 is corresponding to an image display area I1 of thetransparent display 110, and the image light beam IL2 is correspondingto an image display area I2 of the transparent display 110. To be morespecific, the head-mounted display 100 uses the phase modulating of atleast a part of the liquid crystal lens 120 to make the image light beamIL1 and the image light beam IL2 emitted from the transparent display110 pass through the pupil P. Simultaneously, the ambient light beam ALpasses through the transparent display 110 and then passes through thepupil P.

In the embodiment, the second Fresnel lens 140 having positive dioptreand the liquid crystal lens 120 may both adjust the image light beam IL(the image light beam IL1 and the image light beam IL2) emitted from thetransparent display 110 to make the adjustable range of the virtualimage (not shown in FIG. 1A) formed by the displayed image correspondingto the image light beam IL increase. Moreover, the dioptre of the firstFresnel lens 130 and the dioptre of the second Fresnel lens 140 may beadjusted depending on each other, such that the image light beam IL andthe ambient light beam AL are adjusted at the same time. For example,the first Fresnel lens 130 may have a negative dioptre, the secondFresnel lens 140 may have a positive dioptre, and all of the firstFresnel lens 130, the second Fresnel lens 140 and the liquid crystallens 120 may simultaneously adjust the image light beam IL and theambient light beam AL. The image light beam IL is able to pass throughthe pupil P after the image light beam IL sequentially passes throughthe second Fresnel lens 140 and the liquid crystal lens 120.Simultaneously, the ambient light beam AL does not diverge or convergeso as to prevent the image of the outside world corresponding to theambient light beam AL from being distorted after at least a part of theambient light beam AL sequentially passes through the first Fresnel lens130, the transparent display 110, the second Fresnel lens 140, and theliquid crystal lens 120.

In some embodiments, the head-mounted display 100 may not include thesecond Fresnel lens 140. The first Fresnel lens 130 of the head-mounteddisplay 100 also has negative dioptre. In these embodiments, the dioptreof the liquid crystal lens 120 modulated by phase modulating and thedioptre of the first Fresnel lens 130 may be adjusted with each other toprevent the image of the outside world corresponding to the ambientlight beam AL from being distorted, the invention is not limitedthereto. In other embodiments, the dioptre of the first Fresnel lens130, the dioptre of the second Fresnel lens 140, and the dioptre of theliquid crystal lens 120 modulated by phase modulating may be adjusted,so as to adjust the displayed image corresponding to the image lightbeam IL and the image of the outside world corresponding to ambientlight beam AL. Otherwise, in some embodiments, other types of lenses mayalso be adopted, for example, a liquid crystal lens, a general lens, ora lens group may be adopted to replace the first Fresnel lens 130 or thesecond Fresnel lens 140, the invention is also not limited thereto.

In the embodiment, the head-mounted display 100 allows at least a partof the image light beam IL emitted from the transparent display 110passing through a pupil P by phase modulating of at least a part of theliquid crystal lens 120. Therefore, the head-mounted display 100 mayemit the image light beam for displaying and receive the externalambient light beam simultaneously. Furthermore, the phase modulating mayoccur in a part or in the entirety of the liquid crystal lens 120 tomake the image light beam IL used for displaying and the ambient lightbeam AL from the outside world coexist and achieve the AR effect.Otherwise, since the transparent display 110 does not block the viewingangle, the head-mounted display 100 may achieve wide FOV effect. Inaddition, the head-mounted display 100 does not need to mount additionaloptical mirrors group or reflection system that is able to reflect theimage light beam multiple times, thus, the volume of the head-mounteddisplay 100 becomes smaller and the weight of the head-mounted display100 becomes lighter. Besides, the head-mounted display 100 does not needto mount light guiding members having mutually bonded multilayer lightsplitting structure, therefore, the manufacturing process of thehead-mounted display 100 is simplified and is easier to produce thehead-mounted display 100 so as to reduce manufacturing cost. In theembodiment, the head-mounted display 100 includes the first Fresnel lens130, and the transparent display 110 is disposed between the liquidcrystal lens 120 and the first Fresnel lens 130. Therefore, the dioptreof the liquid crystal lens 120 modulated by phase modulating and thedioptre of the first Fresnel lens 130 may be adjusted with each other toprevent the image of the outside world corresponding to the ambientlight beam AL from being distorted. In other words, the head-mounteddisplay 100 may simultaneously display the image from the transparentdisplay 110 and the image of the outside world corresponding to theambient light beam AL, and the image of the outside world correspondingto the ambient light beam AL is not distorted, so as to achieve theideal AR effect.

In some embodiments, the transparent display 110 of the head-mounteddisplay 100 may be designed to have a curved-surface shape, and othercomponents of the head-mounted display 100, such as the liquid crystallens 120, the first Fresnel lens 130, and the second Fresnel lens 140,may also be designed to have a curved-surface shape correspondingly, soas to make the head-mounted display 100 provide a better coverage ratio.Otherwise, in some embodiments, the transparent display 110 and theliquid crystal lens 120 may also be adjusted so that two image lightbeams emitted by the transparent display 110 pass through two pupilsrespectively, wherein each of the image light beams passes through onerespective pupil. When the two pupils are respectively corresponding totwo pupils of two eyes of the user, the user can see three-dimensionaldisplay effect via the appropriate design of the transparent display 110and the liquid crystal lens 120. In these embodiments, the head-mounteddisplay 100 may provide a better three-dimensional AR effect for theuser.

FIG. 1B is another schematic view depicting optical paths of thehead-mounted display in the embodiment in FIG. 1A. Referring to FIG. 1B,in the embodiment, the image light beam IL emitted from the transparentdisplay 110 includes an image light beam IL3, and the image light beamIL3 is corresponding to the image display area I3. The phase modulatingmay occur in the entire liquid crystal lens 120 of the head-mounteddisplay 100 to allow the image light beam IL3 (the image light beam IL)passing through the liquid crystal lens 120 passing through the pupil P.When the pupil P is, for example, the pupil of user's eyes HE, the usermay watch a virtual image VI3 formed by the image light beam IL3 (i.e.,the image light beam IL) corresponding to the image display area I3.Simultaneously, the user may watch the image of the outside world (notshown in FIG. 1B) correspondingly formed by the ambient light beam AL.In the embodiment, the phase modulating occurs in the entire liquidcrystal lens 120, and the phase of the liquid crystal lens 120 iscontinuously modulated. Therefore, the image light beam IL3 emitted fromthe edge of the transparent display 110 to the center of the transparentdisplay 110 may all pass through the pupil P. However, in otherembodiments, the phase of the liquid crystal lens 120 may not becontinuously modulated, the invention is not limited thereto.

FIG. 2 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention. Referring to FIG. 2, inthe embodiment, a head-mounted display 200 is similar to thehead-mounted display 100 in FIG. 1A and FIG. 1B. The elements and therelated description of the head-mounted display 200 are similar to thehead-mounted display 100 in FIG. 1A and FIG. 1B, and will not berepeated. The differences between the head-mounted display 200 and thehead-mounted display 100 are described as followings. The head-mounteddisplay 200 includes a transparent display 210, a liquid crystal lens220, the first Fresnel lens 130, and the second Fresnel lens 140. Thetransparent display 210 is configured to emit the image light beam IL,and the image light beam IL further includes an image light beam IL4 andan image light beam IL5, wherein the image light beam IL4 iscorresponding to an image display area I4, and the image light beam IL5is corresponding to an image display area I5. In addition, thetransparent display 210 has a first area A1 and a second area A2, andthe liquid crystal lens 220 has a third area A3 and a fourth area A4,wherein the first area A1 of the transparent display 210 iscorresponding to the image display area I4 and the second area A2 of thetransparent display 210 is corresponding to the image display area I5.

In the embodiment, the phase modulating of the third area A3 of theliquid crystal lens 220 changes the optical path of the image light beamIL4 emitted from the first area A1 when the image light beam IL4 passesthrough the third area A3. Moreover, the phase modulating of the fourtharea A4 of the liquid crystal lens 220 changes the optical path of theimage light beam IL5 emitted from the second area A2 when the imagelight beam IL5 passes through the fourth area A4. Specifically, thefirst area A1 emits the image light beam IL4, and when the image lightbeam IL4 corresponding to the image display area I4 passes through thethird area A3, the phase modulating occurs in the third area A3 of theliquid crystal lens 220 to change the direction of the image light beamIL4 and converge the image light beam IL4 to pass through the pupil P.In addition, the second area A2 emits the image light beam IL5, and whenthe image light beam IL5 corresponding to the image display area I5passes through the fourth area A4, the phase modulating occurs in thefourth area A4 of the liquid crystal lens 220 to change the direction ofthe image light beam IL5 and converge the image light beam IL5 to passthrough the pupil P. In other words, in the embodiment, the image lightbeam IL4 passing through the third area A3 and the image light beam IL5passing through the fourth area A4 pass through the pupil Psimultaneously.

In the embodiment, the phase modulating in the liquid crystal lens 220is not continuous. When the pupil P is, for example, the pupil of user'seyes HE, the user may watch a virtual image VI4 formed by the imagedisplay area I4 and a virtual image VI5 formed by the image display areaI5. To be more specific, the degree of phase modulating of the thirdarea A3 in the liquid crystal lens 220 is different from the degree ofphase modulating of the fourth area A4 in the liquid crystal lens 220 sothat the virtual image VI4 and the virtual image VI5 are located atdifferent locations. Furthermore, the user can observe that the virtualimage VI4 corresponding to the first area A1 and the virtual image VI5corresponding to the second area A2 have different depths of focus. Inother words, the displayed image of the head-mounted display 200 mayhave a depth of field effect due to the phase modulating in the liquidcrystal lens 220 is not continuous. Otherwise, the head-mounted display200 in the embodiment and the head-mounted display 100 in the embodimentdepicted in FIG. 1A to FIG. 1B have similar technical features. Thehead-mounted display 200 may achieve wide FOV and have a smaller volume,a lighter weight, and a simplified manufacturing process.

FIG. 3A is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention, FIG. 3B is anotherschematic view depicting optical paths of the head-mounted display inthe embodiment in FIG. 3A. Referring to FIG. 3A, in the embodiment, ahead-mounted display 300 is similar to the head-mounted display 100 inFIG. 1A and FIG. 1B. The elements and the related description of thehead-mounted display 300 may refer to the head-mounted display 100 inFIG. 1A and FIG. 1B, and will not be repeated. The differences betweenthe head-mounted display 300 and the head-mounted display 100 aredescribed as followings. The head-mounted display 300 includes atransparent display 310, a liquid crystal lens 320, the first Fresnellens 130, and the second Fresnel lens 140. The transparent display 310is configured to emit the image light beam IL, and the image light beamIL includes an image light beam IL6, wherein the image light beam IL6 iscorresponding to an image display area I6. In addition, the transparentdisplay 310 has a first area A5 and the liquid crystal lens 320 has asecond area A6, wherein the first area A5 of the transparent display 310displays the image display area I6. In the embodiment, the phasemodulating of the second area A6 of the liquid crystal lens 320 allowsthe image light beam IL6 emitted from the first area A5 of thetransparent display 310 passing through the second area A6 and then theimage light beam IL6 passes through the pupil P. To be more specific,the location of the first area A5 is corresponding to the location ofthe second area A6.

Next, referring to FIG. 3B. In the embodiment, the transparent display310 has a first area A7 and the liquid crystal lens 320 has a secondarea A8, wherein the first area A7 of the transparent display 310displays the image display area I7. In the embodiment, the phasechanging of the second area A8 of the liquid crystal lens 320 allows theimage light beam IL7 emitted from the first area A7 of the transparentdisplay 310 passing through the second area A8 and then the image lightbeam IL7 passes through the pupil P. Specifically, the location of thefirst area A7 is not corresponding to the location of the second areaA8, and an asymmetrical opening angle is formed when the image lightbeam IL7 passes through the pupil P. Referring to FIG. 3A and FIG. 3Bsimultaneously, in the embodiment, the first area A5 in FIG. 3A and thefirst area A7 in FIG. 3B may be located at the same location in thetransparent display 310. Within a time sequence, the phase modulatingthat occurs in the second area A6 of the liquid crystal lens 320 (asshown in FIG. 3A) is gradually transformed to the phase modulating thatoccurs in the second area A8 (as shown in FIG. 3B). In other words, thearea of the liquid crystal lens 320 in which the phase modulating occursis gradually changed within a time sequence so that the area of theliquid crystal lens 320 in which the phase modulating occurs affects theimage light beam emitted by the transparent display 310 to formdifferent imaging effects. The area of the liquid crystal lens 320corresponding to the displayed image of the transparent display 310 inwhich the phase modulating occurs is transformed to the area that is notcorresponding to the displayed image of the transparent display 310, andthe area of the liquid crystal lens 320 in which the phase modulatingoccurs is gradually changed within a time sequence. In FIG. 3A, the usermay watch a virtual image VI6 formed by the image display area I6 inFIG. 3A, and the user may watch a virtual image VI7 formed by the imagedisplay area I7 in FIG. 3B. To be more specific, since the asymmetricalopening angle is formed when the image light beam IL7 passes through thepupil P, the user feels like the displayed image of the head-mounteddisplay 300 is moving when watching the displayed image of thehead-mounted display 300 transforming from the virtual image VI6 to thevirtual image VI7. The head-mounted display 300 in the embodiment andthe head-mounted display 100 in the embodiment depicted in FIG. 1A toFIG. 1B have similar technical features. The head-mounted display 300may achieve wide FOV effect and have a smaller volume, a lighter weight,and a simplified manufacturing process.

FIG. 4A is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention, and FIG. 4B is anotherschematic view depicting optical paths of the head-mounted display inthe embodiment in FIG. 4A. Referring to FIG. 4A, in the embodiment, ahead-mounted display 400 is similar to the head-mounted display 100 inFIG. 1A and FIG. 1B. The elements and the related description of thehead-mounted display 400 may refer to the head-mounted display 100 inFIG. 1A and FIG. 1B, and will not be repeated. The differences betweenthe head-mounted display 400 and the head-mounted display 100 aredescribed as followings. The head-mounted display 400 includes atransparent display 110, a liquid crystal lens 420, the first Fresnellens 130, and the second Fresnel lens 140. In the embodiment, thetransparent display 110 is configured to emit an image light beam IL,and the image light beam IL includes an image light beam IL8, whereinthe image light beam IL8 is corresponding to an image display area I8.When the pupil P is, for example, the pupil of user's eyes HE, the usermay watch a virtual image VI8 formed by the image light beam IL8 (theimage light beam IL) corresponding to the image display area I8.

In the embodiment, the head-mounted display 400 adjusts the openingangle of the image light beam passing through the pupil P via adjustingthe degree of phase modulating of at least a part of the liquid crystallens 420. To be more specific, please refer to FIG. 4A and FIG. 4Bsimultaneously. In FIG. 4A, the image light beam IL8 passing through thepupil P is corresponding to the image display area I8, and the imagelight beam IL8 has an opening angle θ₁ to form an image on the retina.When the opening angle increases, the image may expand on the retina.Subsequently, in FIG. 4B, a greater degree of light convergence of theliquid crystal lens 420 in the head-mounted display 400 is achieved toincrease the opening angle of the image light beam passing through thepupil P via adjusting the degree of phase modulating of at least a partof the liquid crystal lens 420. To be more specific, in FIG. 4B, theimage light beam IL8′ passing through the pupil P is corresponding tothe image display area I8, a virtual image VI8′ is also corresponding tothe image display area I8. The image light beam IL8′ has an openingangle θ₂, and the opening angle θ₂ is greater than the opening angle θ₁of the FIG. 4A. At this time, the user may observe that the virtualimage VI8′ is greater than the virtual image VI8. In other words, in theembodiment, the head-mounted display 400 enlarges the displayed image ofthe transparent display 110 via adjusting the degree of phase modulatingof at least a part of the liquid crystal lens 420. In other embodiments,the degree of phase modulating of at least a part of the liquid crystallens 420 in the head-mounted display 400 is adjusted to affect thedisplayed image of the transparent display so as to form other displayeffects, such as image reduction or image translation, etc., theinvention is not limited thereto. To be more specific, the head-mounteddisplay 400 in the embodiment and the head-mounted display 100 in theembodiment depicted in FIG. 1A to FIG. 1B have similar technicalfeatures. The head-mounted display 400 may achieve wide FOV and have asmaller volume, a lighter weight, and a simplified manufacturingprocess.

FIG. 5 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention. Referring to FIG. 5, inthe embodiment, a head-mounted display 500 is similar to thehead-mounted display 100 in FIG. 1A and FIG. 1B. The elements and therelated description of the head-mounted display 500 may refer to thehead-mounted display 100 in FIG. 1A and FIG. 1B, and will not berepeated. The differences between the head-mounted display 500 and thehead-mounted display 100 are described as followings. The head-mounteddisplay 500 includes the transparent display 110, the liquid crystallens 120, the first Fresnel lens 130, and a second Fresnel lens 540.Specifically, the liquid crystal lens 120 is disposed between thetransparent display 110 and the second Fresnel lens 540, and at least apart of the ambient light beam AL received by the first Fresnel lens 130sequentially passes through the transparent display 110, the liquidcrystal lens 120, the second Fresnel lens 540 and then passes throughthe pupil P. In the present embodiment, since the second Fresnel lens540 is not directly disposed beside the transparent display 110, thesecond Fresnel lens 540 is not so close to the transparent display 110that the user may not watch the second Fresnel lens 540. To be morespecific, the user can watch the image displayed by the transparentdisplay 110 but not watch the appearance of the second Fresnel lens 540at the same time because the second Fresnel lens 540 is not close to thetransparent display 110. The head-mounted display 500 in the embodimentand the head-mounted display 100 in the embodiment depicted in FIG. 1Ato FIG. 1B have similar technical features. The head-mounted display 500may achieve wide FOV and have a smaller volume, a lighter weight, and asimplified manufacturing process.

FIG. 6 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention. Referring to FIG. 6, inthe embodiment, a head-mounted display 600 is similar to thehead-mounted display 100 in FIG. 1A and FIG. 1B. The elements and therelated description of the head-mounted display 600 may refer to thehead-mounted display 100 in FIG. 1A and FIG. 1B, and may not berepeated. The differences between the head-mounted display 600 and thehead-mounted display 100 are described as followings. The head-mounteddisplay 600 comprises the transparent display 110, the liquid crystallens 120, a liquid crystal lens 650 and a liquid crystal lens 660. Inthe head-mounted display 600, a liquid crystal lens 650 and a liquidcrystal lens 660 are adopted to replace the first Fresnel lens 130 andthe second Fresnel lens 140 respectively. In the embodiment, the liquidcrystal lens 650 and the liquid crystal lens 660 may achieve anappropriate dioptre via phase modulating. For example, the liquidcrystal lens 650 has a negative dioptre by the phase modulating, and theliquid crystal lens 660 has a positive dioptre by the phase modulating.The head-mounted display 600 in the embodiment and the head-mounteddisplay 100 in the embodiment depicted in FIG. 1A and FIG. 1B havesimilar technical features. The head-mounted display 600 may achievewide FOV and have a smaller volume, a lighter weight, and a simplifiedmanufacturing process.

FIG. 7 is a schematic view depicting optical paths of a head-mounteddisplay in another embodiment of the invention, referring to FIG. 7. Inthe embodiment, a head-mounted display 700 is similar to thehead-mounted display 100 in FIG. 1A and FIG. 1B. The elements and therelated description of the head-mounted display 700 may refer to thehead-mounted display 100 in FIG. 1A and FIG. 1B, and will not berepeated. The differences between the head-mounted display 700 and thehead-mounted display 100 are described as followings. The head-mounteddisplay 700 further includes a liquid crystal panel 770, and thetransparent display 110 is disposed between the liquid crystal lens 120and the liquid crystal panel 770. By the phase modulating of the liquidcrystal panel 770, at least a part of the liquid crystal panel 770blocks the ambient light beam to pass through. To be more specific, thephase modulating occurs in an area A of the liquid crystal panel 770 sothat a part of the ambient light beam AL′ is unable to pass through thearea A. In contrast, except the area A, the phase modulating does notoccur in the remaining area of the liquid crystal panel 770. Therefore,the ambient light beam AL may successfully pass through the remainingarea of the liquid crystal panel 770. In the embodiment, the location ofthe area A may be corresponding to the image display area of thetransparent display 110, for example, the location of the area A iscorresponding to the location of the image display area I2. When theuser watch the virtual image (not shown) formed by the image light beamIL2 (the image light beam IL) corresponding to the image display areaI2, the virtual image formed by the image light beam IL2 is notoverlapped with the image of the outside world (not shown in FIG. 7)corresponding to the ambient light beam AL′. Therefore, the image of theoutside world corresponding to the ambient light beam AL′ does notinterfere with the virtual image formed by the image light beam IL2 sothat a more distinct display effect is achieved when the user watchesthe virtual image corresponding to the image display area I2. Incontrast, since the ambient light beam AL may successfully pass throughthe area of the liquid crystal panel 770 except the area A, when theuser watch the virtual image (not shown in FIG. 7) formed by the imagelight beam IL1 (the image light beam IL) corresponding to the imagedisplay area I1, the virtual image formed by the image light beam IL1 isoverlapped with the image of the outside world corresponding to theambient light beam AL. To be more specific, by the phase modulating ofthe liquid crystal panel 770, at least a part of the liquid crystalpanel 770 blocks the ambient light beam to pass according to actualrequirements. In some embodiments, the phase modulating may also occurin the entire liquid crystal panel 770 to prevent the ambient light beamfrom passing through, such that the user cannot see the ambient lightbeam corresponding to the image of the outside world when the user wearsthe head-mounted display. At the same time, the head-mounted display mayachieve the VR effect. The head-mounted display 700 in the embodimentand the head-mounted display 100 in the embodiment depicted in FIG. 1Aand FIG. 1B have similar technical features. The head-mounted display700 may achieve wide FOV and have a smaller volume, a lighter weight,and a simplified manufacturing process.

In summary, the embodiments of the invention have at least one of theadvantages or effects below. In an embodiment of the invention, thetransparent display of the head-mounted display is disposed between theliquid crystal lens and the first Fresnel lens. The transparent displayis configured to emit the image light beam, and the first Fresnel lensis configured to receive the ambient light beam. The head-mounteddisplay uses the phase modulating of at least a part of the liquidcrystal lens to allow at least a part of the image light beam emittedfrom the transparent display passing through a pupil. Therefore, thehead-mounted display may emit the image light beam used for displayingand receive the external ambient light beam at the same dine, and thephase modulating may occur in a part or in entire of the liquid crystallens to allow the image light beam used for displaying and the externalambient light beam coexist and achieve the AR effect. Since thetransparent display does not cause the problem that the viewing angle isblocked, the head-mounted display may achieve wide FOV. Otherwise, thehead-mounted display does not need to reflect the image light beammultiple times based on the group of optical mirrors or the reflectionsystem, thus, the volume of the head-mounted display becomes smaller andthe weight of the head-mounted display becomes lighter. Besides, thehead-mounted display does not need to guide the image beam through thelight guiding member having mutually bonded multilayer light splittingstructure, therefore, the manufacturing process of the head-mounteddisplay is simplified and it is easier to produce the head-mounteddisplay.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of theinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the invention covermodifications and variations of this invention provided they fall withinthe scope of the following claims and their equivalents. The abstract ofthe disclosure is provided to comply with the rules requiring anabstract, which will allow a searcher to quickly ascertain the subjectmatter of the technical disclosure of any patent issued from thisdisclosure. It is submitted with the understanding that it will not beused to interpret or limit the scope or meaning of the claims. Anyadvantages and benefits described may not apply to all embodiments ofthe invention. It should be appreciated that variations may be made inthe embodiments described by persons skilled in the art withoutdeparting from the scope of the present invention as defined by thefollowing claims. Moreover, “first”, “second”, “third”, “fourth” etc.mentioned in the specification and the claims are merely used to namethe elements and should not be regarded as limiting the upper or lowerbound of the number of the components/devices.

What is claimed is:
 1. A head-mounted display, comprising: a transparentdisplay, configured to emit an image light beam; a liquid crystal lens,disposed near the transparent display; and a first Fresnel lens, whereinthe transparent display is disposed between the liquid crystal lens andthe first Fresnel lens, the first Fresnel lens is adapted to receive anambient light beam, and wherein the head-mounted display is adapted toallow at least a part of the image light beam emitted from thetransparent display passing through a pupil by phase modulating of atleast a part of the liquid crystal lens.
 2. The head-mounted display asrecited in claim 1, wherein the transparent display comprises a firstarea, and the liquid crystal lens comprises a third area, and the phasemodulating of the third area of the liquid crystal lens makes the imagelight beam emitted from the first area of the transparent display passthrough the third area of the liquid crystal lens, and then the imagelight beam passes through the pupil, wherein a location of the firstarea is corresponding to a location of the third area.
 3. Thehead-mounted display as recited in claim 1, wherein the transparentdisplay comprises a first area, and the liquid crystal lens comprises athird area, and the phase modulating of the third area of the liquidcrystal lens makes the image light beam emitted from the first area ofthe transparent display pass through the third area of the liquidcrystal lens and then the image light beam passes through the pupil,wherein a location of the first area is not corresponding to a locationof the third area.
 4. The head-mounted display as recited in claim 1,wherein the phase modulating of the liquid crystal lens is continuous.5. The head-mounted display as recited in claim 1, wherein thetransparent display has a first area and a second area, and the liquidcrystal lens has a third area and a fourth area, the phase modulating ofthe third area of the liquid crystal lens changes optical path of theimage light beam emitted from the first area when the image light beampasses through the third area, the phase modulating of the fourth areaof the liquid crystal lens changes optical path of the image light beamemitted from the second area when the image light beam passes throughthe fourth area, wherein the image light beam passing through the thirdarea and the image light beam passing through the fourth area passthrough the pupil.
 6. The head-mounted display as recited in claim 5,wherein a degree of phase modulating of the third area of the liquidcrystal lens is different from a degree of phase modulating of thefourth area of the liquid crystal lens.
 7. The head-mounted display asrecited in claim 1, wherein an opening angle of the image light beampassing through the pupil is adjusted by adjusting a degree of phasemodulating of at least a part of the liquid crystal lens.
 8. Thehead-mounted display as recited in claim 1, wherein the first Fresnellens is adapted to receive the ambient light beam, and at least a partof the ambient light beam passes through the transparent display and thepupil.
 9. The head-mounted display as recited in claim 1, wherein thefirst Fresnel lens has a negative dioptre.
 10. The head-mounted displayas recited in claim 1, further comprising a second Fresnel lens, whereinthe second Fresnel lens has a positive dioptre, the transparent displayis disposed between the first Fresnel lens and the second Fresnel lens,and at least a part of the ambient light beam passing through the firstFresnel lens sequentially passes through the transparent display, thesecond Fresnel lens, the liquid crystal lens and the pupil.
 11. Thehead-mounted display as recited in claim 1, further comprising a secondFresnel lens, wherein the second Fresnel lens has a positive dioptre,the liquid crystal lens is disposed between the transparent display andthe second Fresnel lens, and at least a part of the ambient light beampassing the first Fresnel lens sequentially passes through thetransparent display, the liquid crystal lens, the second Fresnel lensand the pupil.
 12. The head-mounted display as recited in claim 1,further comprising a liquid crystal panel, wherein the transparentdisplay is disposed between the liquid crystal lens and the liquidcrystal panel, and the ambient light beam is blocked by at least a partof the liquid crystal panel according to the phase modulating of theliquid crystal panel.